The present invention relates generally to thermal insulation technology. More particularly, the invention provides a layered structure to an optical reflector. Merely by way of example, the invention has been applied to a satellite system, but it would be recognized that the invention has a much broader range of applicability.
A satellite uses thermal insulation to control the internal temperature of the satellite. The internal temperature should be maintained so that various instruments in the satellite can function properly. The satellite instruments usually include sensitive electronic systems susceptible to malfunctions caused by thermal variations. Hence the high-quality thermal insulation is important for proper functioning of the satellite.
One type of thermal insulation used by satellite includes an optical solar reflector. The optical solar reflector protects an exterior surface of the satellite. To control the internal temperature of the satellite, the optical solar reflector suppresses the absorption of heat from the solar radiation and facilitate the radiation of heat from the satellite. For example, the optical solar reflector reflects solar energy incident on the satellite and emits heat energy produced by the satellite. Consequently, the optical solar reflector should usually have a low ratio of absorption coefficient to emissivity.
Also, the optical solar reflector should have high environmental stability and mechanical integrity. The environmental stability can ensure longitivity of the optical solar reflector. The optical solar reflector needs to function properly for the lifetime of the satellite; otherwise, the satellite instruments may malfunction prematurely. Similarly, the mechanical integrity can ensure sufficient coverage of the solar optical reflector on the satellite. For example, the optical solar reflector should have sufficient mechanical integrity to cover both curved surfaces and flat surfaces of the satellite; otherwise, the exposed curved surfaces may cause the malfunction of the satellite.
The conventional optical solar reflector usually cannot meet both criteria of high environmental stability and mechanical integrity. For example, an optical solar reflector may be a flexible optical solar reflector that includes a polymer-based heat radiation layer. But the flexible optical solar reflector usually suffers from deterioration of the polymer layer under the radiation of solar energy. Hence the optical reflector does not have sufficient environmental stability. As another example, an optical reflector may be a rigid optical solar reflector which includes a glass-based heat radiation layer. The rigid optical solar reflector is usually flat; therefore it can be used only at limited locations on the satellite. Further, the rigid solar reflector is usually difficult to handle during manufacturing and assembling. Hence the rigid optical solar reflector lacks desirable mechanical integrity.
It is desirable to improve an optical solar reflector.